1. Field of the Invention
The present invention relates to a focusing control device, a focusing control method, a focusing control program, a lens device, and an imaging device.
2. Description of the Related Art
In recent years, with an increase in resolution of imaging elements, such as a charge coupled device (CCD) image sensor and a complementary metal oxide semiconductor (CMOS) image sensor, there is a rapid increase in demand for electronic devices having an imaging function, such as a digital still camera, a digital video camera, and a mobile phone, such as a smartphone. The electronic devices having an imaging function described above are referred to as imaging devices.
In these imaging devices, as a focusing control method which focuses on a main subject, a contrast auto focus (AF) method or a phase difference AF method (for example, see JP2012-137547A and JP2014-85503A) is employed. Since the phase difference AF method can perform high-speed processing, the phase difference AF method is a method effective for moving image capturing where a subject is continuously imaged with an imaging element.
In the phase difference AF method, correlation calculation for calculating a correlation value while deviating signal groups according to a pair of luminous fluxes passing through different portions of a pupil area of an imaging optical system from each other is performed, and the phase difference between the two signal groups is detected based on the result of the correlation calculation.
In order to exclude the influence of offset between two signal groups, JP2012-137547A describes that differential filter processing is performed on each of the two signal groups before correlation calculation.